The objective of this project is to develop a porcine model for the study of Campylobacter pyloridis in the pathogenesis of gastric ulcers and evaluate the role of Campylobacter pyloridis infections in the pathogenesis of histamine and prednisone induced gastric ulcers in gnotobiotic pigs. Specific aims of this project are: 1) Determine the minimum infective dose of C. pyloridis in gnotobiotic pigs and investigate its ecological niche in the pig; 2) Investigate the effect of C. pyloridis infection on the pathogenesis of histamine-induced gastric ulcers in pigs; 3) Determine the role of C. pyloridis in the pathogenesis of prednisone-induced gastric ulcers in pigs. This study will utilize 4-week-old cesarean-derived gnotobiotic pigs. All treated pigs will be inoculated per os at 2 or 4 weeks of age and will be killed at 24 hour intervals starting on post-inoculation-day 1. Evaluation of experimental animals will include: gross pathology, light microscopy, scanning electron microscopy, transmission electron microscopy and microbiology. Microbiological studies will include quantitation of bacteria on the mucosal surface of the distal esophagus, stomach, duodenum, jejunum, ileum, cecum, colon and in gastric juice.